Methods for the manufacture of mixed polyamide yarns

ABSTRACT

The invention provides a method of making a polyamide mixed yarn comprising: simultaneously spinning a first group of filaments of a first polyamide and a second group of filaments of a second polyamide different from the first polyamide; combining the first and second groups of filaments through an air interlacing jet; and winding up the interlaced filaments. The invention also provides mixed yarns obtainable by the method of the invention, and fabrics and garments containing the yarns.

The present invention relates to methods for the manufacture of mixedpolyamide yarns for apparel textile end-uses, and to mixed yarns,textiles and garments obtainable thereby.

It is desirable to provide textile materials, especially for apparelend-uses, that comprise filaments of more than one kind of polymer. Inparticular, if the textile contains a plurality of different filamentshaving different dye affinities, then attractive visual effects can beachieved on dyeing the textile.

It is known to provide such mixed textile materials by weaving thetextile with more than one kind of yarn. It is also known to provideyarns of bicomponent filaments, for example filaments having a sheath ofa first polymer and a core of a second polymer. Finally, it is known toprovide mixed-filament yarns by intermingling multifilament yarns spunfrom different materials on a texturizing machine. However, this methodis not entirely satisfactory and is limited to the production oftexturised mixed yarns.

Accordingly, it would be desirable to develop new mixed textile yarns,in particular polyamide yarns, for apparel applications that could bemanufactured quickly and cheaply.

The vast majority of nylon (polyamide) fabrics are dyed with so-calledanionic dyes that have a special affinity for the amine end groups ofthe yarn. Typically, anionic dyeable polyamides contain at least about30, more typically about 40 to 60, and up to about 80 amine end groupequivalents (AEG) per 10⁶ grams of polymer. Such dyes include acid dyes,premetallised dyes, reactive dyes and so on.

It is also known that nylon yarns, which are normally strongly dyed byanionic dyestuffs, can be rendered resistant to such dyestuffs bymodifying the polymer chemistry. The agents used to modify the polyamideinclude bifunctional carboxylic acids, and especially sulphonatedorganic bifunctional acids and their esters. See for example U.S. Pat.No. 4,075,378; assigned to E. I. du Pont de Nemours and Company). Suchyarns are referred to as cationic-dyeable yarns, or conveniently ascat-dye yarns, and sometimes as base-dye yarns. These yarns normallycontain less than about 40 and more typically 15 amine end groupequivalents per 10⁶ grams of polymer. Typically, cationic dyeablepolyamides contain at least about 50 and more preferably about 70 to 150aromatic sulphonate group equivalents per 10⁶ grams of polymer.Cationic-dye yarns are known in the manufacture of carpets, where it ispossible to combine them with standard anioniodyeable yarns to produce atwo-colour heather or marl effect.

The use of cationic dyeable yarns for apparel end uses is much rarer,though not unknown. Thus there have been various commercial cat-dyeyarns over the years, e.g. U.S. Pat. No. 3,682,866; assigned to ImperialChemical Inds. PLC and U.S. Pat. No. 3,707,344; assigned to BASF. Thecommon feature of these yarns is that they were made by fairlyslow-speed spinning through a conventional two-stage route. It is knownthat the cationic-dyeable nylon polymers spin less well, and with higherinterruption rates, than standard anionic dyeable nylon, even in theproduction of carpet yarns. The lighter decitex yarns used for appareltextiles, the much finer filaments, and the very large strain ratesassociated with high speed spinning have until now precluded the use ofcat-dye polymers for apparel end-use. This has remained the case, eventhough such yarns, especially when used in combination withconventional-dye nylon, are clearly highly desirable, and offer a greatvariety of effects in fabric form. A particularly desirable product is acat-dye nylon partially oriented yarn (POY) which could be used fortexturing with a standard-dye yarn to give a textured two-tone heatheror marl yarn after dyeing.

A more efficient and higher speed means to spin textile yarns dyeablewith cationic dyes is desired in the art. Higher speed spinning meansand the products of these high speed processes are disclosed herein. Bymeans of the present invention it is possible to spin both POY and highspeed fully-drawn polyamide yarns (FDY) of high cationic dye affinity atsuperior interruption (filament breakage) rates for a commercialmelt-spinning process. Furthermore, the means of filament spinningdisclosed herein make it possible to spin critical yarns of fine singlefilament titre and especially those yarns with filaments of non-circularprofiled cross-section.

It has been found by the present inventors that it is possible to spinboth POY and high-speed fully-drawn (FDY) mixed polyamide yarns of highcationic-dye affinity at interruption rates acceptable for a commercialmelt-spinning process, and that furthermore it is even possible to spinmixed critical yarns, such as yarns containing filaments of finefilament titre, and of non-circular, profiled cross-section. This isachieved by spinning the different filaments of the mixture fromseparate spinning packs in a spinning machine, and interlacing thefilaments in the spinning machine by means of an air interlacing jetafter the filaments have solidified but before they are wound up.

Accordingly, the present invention provides a method of making apolyamide mixed yarn comprising: simultaneously spinning a first groupof filaments of a first polyamide and a second group of filaments of asecond polyamide different from the first polyamide; combining the firstand second groups of filaments through an air interlacing jet; andwinding up the interlaced filaments.

The yarns made by the method of the invention are normally textile yarnsthat are especially useful for apparel fabric applications. That is tosay, yarns having a yarn weight of from about 5 to about 300 dtex, afilament weight of from about 0.5 to about 7 dtex. Preferably, the yarncomprises from about 3 to about 136 filaments.

Preferably, the yarns have a filament uniformity in Uster % of about1.5% or less, more preferably about 1% or less. This is desirable inorder for the yarn to have the high appearance uniformity needed forapparel applications, and also to reduce yarn breaks in texturing,weaving and knitting operations.

Preferably, the yarns have an elongation to break of from about 20 toabout 90%. Preferably, the yarns have a tenacity of from about 25 toabout 65 cN/tex. These tensile properties are all desirable for appareltextile applications.

In certain embodiments, the first polyamide has a titanium dioxidecontent less than 0.1% and preferably less than 0.01% by weight and thesecond polyamide has a titanium dioxide content greater than 0.3% andpreferably greater than 1.0% by weight. This gives a mixed yarncontaining bright filament highlights from the clear or bright firstcomponent enhanced against the matt or dull second component.

In certain embodiments the first polyamide and the second polyamide havedifferent dyeing characteristics with anionic dyes or cationic dyes.These dyeing characteristics may arise from different numbers of amineend groups. For example, the first polyamide and the second polyamidemay differ by at least 8 mols per 10⁶ g in the concentration of amineend groups (AEG), more preferably at least 12 mols per 10⁶ g and morepreferably at least 15 mols per 10⁶ g. The AEG number influences howdeeply the polyamide is dyed by anionic dyes. Alternatively oradditionally, one of the polyamides may contain anionic end groups, suchas sulfonate or carboxylate end groups, that render the polyamidecationic-dyeable.

In certain embodiments the first polyamide comprises a cationic-dyepolyamide and the second polyamide comprises an anionic-dye polyamide.Preferably, the cationic-dye polyamide has at least 50 anionic endgroups per 10⁶ g (AEG). The method according to the invention therebymakes possible for the first time the high speed spinning of apparelyarns that can achieve heather or marl dyeing effects.

In certain embodiments the filaments of the first polyamide and thefilaments of the second polyamide in the product yarn exhibit anabsolute difference of at least 10% in their boiling water shrinkagevalues as hereinafter defined. This gives the effect that, in subsequentheat treatment, the high shrink filaments contract, and the lower shrinkfilaments then stand out to give a bulked or texturised appearance andhand to the yarn or fabric.

For example, the amine component of the first polyamide compriseshexamethylene diamine and the second polyamide is a copolymer in whichthe amine component comprises a mixture of hexamethylene diamine with atleast 20% by weight of methyl pentamethylene diamine based on the totalweight of diamine. Preferably, the diamine components of the first andsecond polyamides are substantially or essentially made up ofhexamethylene diamine and hexamethylene diamine/20% methylpentamethylene diamine. In other embodiments, one of the polyamides maycomprise nylon 6 and the other polyamide may comprise nylon 66.

In certain embodiments, one of the said groups of filaments has acircular filament cross-section and the other of the said groups offilaments has a non-circular filament cross-section. This enablesfurther interesting visual effects to be achieved in the same high speedspinning process.

Preferably, the non circular filaments have an individual filamentdecitex of greater than 2.5 and the circular filaments have individualdecitex less than 2.

In certain preferred embodiments the non-circular filaments are trilobalwith modification ratio greater than 1.2 and less than 2.4, preferablyfrom about 1.4 to about 1.8. The modification ratio is defined as theratio of the radius of the smallest circle that circumscribes theprofile to the radius of the largest circle that is completely inscribedin the profile.

In other embodiments, the filament cross-section is elongated.Preferably, the cross-section has a two-fold axis of rotationalsymmetry. For example, the filament cross-section may be selected fromthe group consisting of oval, tape or diabolo shapes. Preferably, thelength ratio (Aspect Ratio) of the longest axis of the elongatedfilament cross-section to the shortest axis at right angles to thatlongest axis is greater than about 1.5.

In preferred embodiments, the first group of filaments is bright andtrilobal with filament decitex greater than 2.5, modification ratiobetween 1.4 and 1.8 and made with basic dye polymer and the second groupof filaments is dull and circular with filament decitex less than 2 andmade with acid dye polymer.

The first and second pluralities of filaments are spun in substantiallyconventional fashion through laterally spaced first and secondpluralities of spinneret holes that are fed with the molten first andsecond polyamides, respectively. The dimensions of the spinneret holes,melt velocity, temperature, wind-up speed and other spinning conditionsare selected in conventional fashion to produce the desired filamentproperties such as shape, weight, uniformity, and tenacity. The factthat the pluralities of filaments are interlaced introduces thelimitation that the wind-up speed is by definition the same for the twopluralities of filaments.

Interlacing, also known as intermingling or entangling, is the processwhereby the substantially parallel filaments of a freshly spunmultifilament yarn are given coherence by inducing periodically spacedknots or nodes separated by portions of lesser filament entanglement.This periodic node structure is produced by passing the filamentsthrough a fluid jet, the fluid typically being compressed air. Theinterlace introduces coherence among the filaments of the yarn.

Apparatus for interlacing multifilament yarns includes the Model FG3from Fibreguide Ltd., Cheshire, U.K., and the Heberlein Polyjet SP fromHeberlein Maschinenfabrik AG, Wattwil, Switzerland. The HeberleinPolyjet-SP-25 model H133/C14 was used in the following examples.Typically the air pressure supplied to the air jet interlace apparatusis from 55 to 200 kPa (8 to 30 psi). The level of interlacing generallyincreases with increase in air pressure and reduction in yarn tension.

The pluralities of filaments may be intermingled individually to providestronger linking of the filaments of each component before interminglingtogether. This provides a strong marl with a streaky appearance in thefinal fabric. Omission of this step causes the filaments to mixintimately when combined to give a shorter term heathe appearance infabric. The appropriate level of component and combinatio interminglingcan readily be determined experimentally for the particular procesconditions to give the appearance desired.

The yarns made in accordance with the present invention preferably havefrom 6 to 40 interlace nodes per meter.

The methods according to the present invention may further comprise thestep of texturing the mixed polyamide yarn by false twist texturing orair-jet texturing.

Preferably, the yarn is wound up at a speed of at least 3000 m/min, morepreferably at least 3500 m/min and most preferably at a speed of atleast 4000 m/min. This high speed spinning, which has not hitherto beenpractised with cationic-dye polyamides, provides high yarn output andalso provides a degree of orientation of the filaments.

In some embodiments, the yarn is wound up at high speed substantiallywithout an intermediate drawing step, whereby the yarn is a partiallyoriented yarn (POY).

In other embodiments, the yarn is wound up at high speed with anintermediate drawing step. Preferably this results in a fully drawn yarn(FDY).

In a second aspect, the present invention provides a mixed polyamideyarn obtainable by a method according to the present invention andcomprising a first group of filaments of a first polyamide interlacedwith a second group of filaments of a second polyamide different fromthe first polyamide.

Preferably, the yarn according to the present invention is a flat yarn,but it may alternatively be a textured yarn, or a flat yarn combiningfilaments of different shrinkages to produce a textured appearance andhandle when subjected to subsequent dyeing and finishing operations.

In a third aspect, the present invention provides a textile fabriccomprising a yarn according to the invention. For example the textilefabric may be a woven, nonwoven or knitted textile fabric, preferably anapparel fabric.

In certain embodiments the fabric according to the present inventioncomprises cationic-dye polyamide and has been dyed with a cationicdyestuff. Where the fabric comprises a yarn that is a mixture ofcationic-dye and anionic-dye filaments, the present invention preferablyprovides fabrics that have been dyed with both cationic and anionicdyes, preferably in the same dyeing bath. Such fabrics exhibitespecially interesting colour effects.

In a fourth aspect the present invention provides a garment comprising afabric according to the present invention in a visible portion thereof.

Specific embodiments of the present invention will now be describedfurther by way of example, with reference to the accompanying drawing,in which:

FIG. 1 is a schematic of a preferred process for the high speed spinningof the cationic dyeable polyamide yarns in accordance with the presentinvention.

Here and elsewhere in the present specification the parameters of theprocess and the yarns are measured as follows.

Yarn & polymer relative viscosities were measured at 25 degrees C. using8.4% w/w solution of the yarn in formic acid containing 10% water (ASTMD789). The instrument used was an automated capillary viscometer of thetimed-flow, U-tube type.

Yarn Decitex (the linear density) was measured at 20 degrees C. and 65%relative humidity using a wrap-wheel & weighing balance, according tothe BISFA “Internationally agreed methods for testing polyamide filamentyarns”-1995.

Yarn linear density evenness, also known as the yarn Uster percent (U%), was determined using a Uster evenness tester 3, type C.

The oil on yarn percentage was determined using a Bruker NMR (NuclearMagnetic Resonance) minispec pc-120 instrument. Calibration was madeagainst known standards where oil level had been measured by extractingoil from the yarn by hot petroleum ether, evaporating, and weighing theresidue.

Yarn tensile properties (breaking force, tenacity, percentage extensionto break and the derived parameter T*RE where T is the tenacity which ismultiplied by RE, the square root of the extension to break) weremeasured on an Instron Tensile Tester model 4301 using conditions statedin the BISFA “Internationally agreed methods for testing polyamidefilament yarns”-1995.

Interlace is measured according to ASTM standard method D4724-87(reapproved 1992). This method covers common procedures for interlacemeasurement by needle insertion. The results are reported as interlacenodes per meter of interlaced yarn. A suitable apparatus to measureinterlace nodes is the Rothschild R2071/72 automated interlace testerfrom Rothschild Measurement Instruments, Traubenstrasse 3, Zurich,Switzerland.

Boiling water shrinkage was measured according to BISFA “Internationallyagreed methods for testing polyamide filament yarns”-1995

Referring to FIG. 1, at 10 or 10′ first and second molten polymers areintroduced to polymer filter spin packs (12,12′) and metered throughspinneret plates (14,14′) to form two spatially separated pluralities offilaments (18,18′) having different filament cross sections. Thefilaments are quenched via a side stream of conditioned air in quenchchimneys (16,16′). Preferably the emerging filaments are cooled in twoseparate chimneys, so that quench flow rate and other parameters(convergence distance etc.) can be optimised for each componentseparately. The quenched filaments are converged, preferably separately,into a yarn at a convergence guide (20,20′) and oiled at a roll (22,22′)to form a spin finished prepared yarn (24,24′) which is interlaced at 25by air jet interlace means.

The interlaced yarn may take Path A to ultimately form an FDY or takePath B to form a POY. Following along Path A, the yarn is withdrawn fromthe quench chimney by feed roll assembly 26, shown diagrammatically as asingle roll, and drawn by roll assembly 28, also shown diagrammaticallyas a single roll, which has a surface speed greater than roll assembly26. The drawn yarn is relaxed with atmospheric steam at 32 andoptionally intermingled by means of 34 and wound up into a package offully drawn yarn 36. Following along Path B, the yarn is withdrawn fromthe quench chimney 16′ by feed and yarn tension management roll assembly26′ and 28′. The “S-wrap” configuration provides for good yarn tensionmanagement during the winding phase and the intermingler stage 34′ isoptionally applied before winding up a package of POY 36′.

In the POY spinning process the Godet rolls to control tension areoptional. An component intermingling step may be before the first rollfollowed by the combination intermingler before, between or after therolls in a POY process.

In the FDY process the air interlace jet may be provided before the drawrolls, or after the relax device, or at any other stage before winding.(Interlacing between the feed and draw rolls is not preferred, becauseof the high tensions associated with drawing the yarn.)

EXAMPLE 1

The following group of experiments illustrates the possibility ofproducing a combined or hetero-yarn, by an economical POY or FDY route,on a single spinning machine, without recourse to separate winding andrecombination of the cat-dye and anionic-dye component yarns.

In general, two separate polymers, one of standard (anionic) dyepolyamide, and the other of cationic-dye polyamide, were independentlymelted, and separately forwarded via independant metering pumps to twoadjacent packs on the spinning machine. The spinnerets of the two packswere variously of the same design, or of different design to allowcombinations of different filament cross sections to add a furtherdimension to the differentiated appearance of the yarn. The emergingmolten filaments were cooled by a stream of quench air, converged andoiled on spin finish applicators, and combined through an airinterlacing jet.

In the case of POY yarns the combined hetero-yarn was then led as asimple S-wrap over a pair of Godet rolls, and finally wound up as abobbin on a high speed winder. The use of the Godet rolls isadvantageous in order to control the yarn tension and package build, butnot essential.

In the case of drawn yarns, the combined hetero-yarn was forwarded tomake several turns round a set of Godet rolls (feed rolls), the numberof turns being sufficient to prevent slippage over these rolls, thenpassed over another set of rolls (draw rolls) revolving at sufficientspeed to stretch the yarn by a predetermined amount (the draw ratio),and finally heat set with a steam-box. The yarn was finally wound up ata speed in excess of 3000 meters per minute. Optionally, an alternativesetting method could have been used, such as heated rolls, and anadditional set of Godet rolls may be incorporated between draw rolls andwinder to control the tension while the yarn is set or relaxed.Optionally also a second application of spin finish, and/or additionalinterlacing may be applied before the final winding step.

The cationic-dye polyamides contain a sulphonic acid functional group,introduced by the incorporation of the sodium salt of5-sulpho-isophthalic acid (molecular weight 268). The specific polymersused had the properties listed in Table 1. Details of the additional,anionic-dyeable polymers used for these hetero-yarns are given in Table1, and specific yarn examples and spinning details in Table 2.

It can be seen from Table 2 that a wide variety of hetero-yarns isexemplified. These include combinations of:

-   -   Cationic and anionic dyeable yarns (all the above);    -   cationic and deep-dye anionic (high AEG) yarns (G, H);    -   cationic dye and high shrinkage anionic dye yarns (I);    -   POY yarns (D to H) and FDY (A to C and I); and    -   Round/round cross-section (A, I), round/diabolo (B,F),        round/trilobal (C,D,H).

Though the scale of the trials was too small to give a preciseindication of spinning interruption rate, there were no indications ofserious spinning difficulties. Extrusion was clean, and the spinneretface showed no more contamination than is usual with standard high speedprocesses. Yarn uniformity levels were good, with Uster % values ofabout 0.8%, and the bobbins of yarn were free from gross loops.

The yarns spun from anionic dyeable/cationic dyeable filamentcombinations were knitted into hoselegs, and each hose-leg was dyed in asingle dye-bath operation using a suitable combination of anionic dyeand cationic dye together in the same bath. The dyeing was typicallycarried out at 100 degrees C. for 1 hour at pH 5.0 in the presence of ananti-precipitating agent to prevent interaction between the two dyes.

The dyed hoselegs had a most attractive heather or marl appearance, eachyarn taking up the appropriate dyestuff. By selecting particulardyestuffs, the colour contrast could be varied from subtle to strong,and further variation could be added by combining different yarn crosssections, varying the different filament titres, and adjusting thedegree of intermingling.

TABLE 1 Polymer RV AEG —SO₃H % TiO₂ Cat-1 31.5 41 55 0.02 Cat-2 45 45 720.27 AN-1 40 50 0 0.009 AN-2 40 50 0 1.0 AN-3 40 70 0 1.6 AN-4* 44 45 00.3 *Polyamide AN-4 is a copolyamide of adipic acid andhexamethylenediamine with 20% of methylpentamethylenediamine.

TABLE 2 Experiment A B C D E F G H I Yarn type FDY FDY FDY POY POY POYPOY POY FDY Decitex 156 156 156 156 156 156 156 156 156 Filaments 88 4671 71 71 77 88 71 88 Anionic Dye 78f68 78f26 78f51 78f51 78f51 78f5178f20 78f20 78f20 Component Cross section* R D TR TR R R R R R AnionicDye AN-1 AN-1 AN-1 AN-1 AN-2 AN-2 AN-3 AN-3 AN-4 Polyamide Cationic Dye78f20 78f20 78f20 78f20 78f20 78f26 78f68 78f51 78f68 Component Crosssection* R R R R TR D R TR R Cationic Dye CAT-2 CAT-2 CAT-2 CAT-2 CAT-1CAT-1 CAT-2 CAT-2 CAT-1 Polyamide Extrusion 280 279 280 280 278 279 280280 278 Temperature (C.) Quench air .35 .35 .35 .35 .40 .40 .35 .35 .35Velocity (m/min) Draw ratio 1.6 1.6 1.6 1 1 1 1 1 1.6 Wind speed 42004200 4200 4200 4200 4200 4200 4200 4200 (m/min) Tenacity (cN/tex) 44 4344 32 34 33 32 30 39 Extensibility % 49 48 47 74 66 68 73 72 53 *Crosssections: R = round or circular; TR = trilobal; D = diabolo or bilobal.

More subtle colour or shade variants were produced by combining yarnswith the same type of dye affinity, but differing in cross-section,content of titanium dioxide delustrant, depth of dyeing characteristicfrom differing concentrations of amine end groups, or using otherpolymer variants such as a nylon 6 yarn combined with nylon 66.

Yarn I in Table 2 exemplifies yarns according to the inventioncontaining both high and low shrinkage polyamide components. The yarnwas knitted into a hoseleg and dyed in an anionic dyestuff. The fabricafter dyeing had a bulked-up textured appearance and feel resulting fromthe differential shrinkage of the yarns

The above embodiments have been described by way of example only. Manyother embodiments of the invention falling within the scope of theaccompanying claims will be apparent to the skilled reader.

1. A method of making a polyamide mixed yarn comprising: simultaneouslyspinning from separate spinning packs, a first group of filaments of afirst polyamide and a second group of filaments of a second polyamidedifferent from the first polyamide, wherein the first polyamide is acationic-dye polyamide and the second polyamide is an anionic-dyepolyamide; combining the first and second groups of filaments through anair interlacing jet; and winding up the interlaced filaments; whereinsaid yarn has yarn weight from about 5 to about 300 dtex.
 2. The methodaccording to claim 1, wherein the first polyamide has a titanium dioxidecontent less than 0.1% by weight and the second polyamide has a titaniumdioxide content greater than 0.3% by weight.
 3. The method according toclaim 2, wherein the first polyamide has a titanium dioxide content lessthan 0.01% by weight and the second polyamide has a titanium dioxidecontent greater than 1.0% by weight.
 4. The method according to claim 2,wherein the first polyamide and the second polyamide have differentdyeing characteristics with anionic dyes or cationic dyes.
 5. The methodaccording to claim 4, wherein the first polyamide and the secondpolyamide differ by at least 8 mols per 10⁶ g in the concentration ofamine end groups (AEG).
 6. The method according to claim 2, wherein thefilaments of the first polyamide and the filaments of the secondpolyamide in the product yarn exhibit a difference of at least 10% intheir boiling water shrinkage values.
 7. The method according to claim2, wherein the amine component of the first polyamide compriseshexamethylene diamine and the second polyamide is a copolymer in whichthe amine component consists comprises a mixture of hexamethylenediamine with at least 20% by weight of methyl pentamethylene diaminebased on the total weight of diamine.
 8. The method according to claim2, wherein one of the said groups of filaments is has a circularfilament cross-section and the other of the said groups of filaments hasa non-circular filament cross-section.
 9. The method according to claim8, wherein the filaments with noncircular filament cross-section have anindividual filament decitex of greater than 2.5 and the filaments withthe circular filament cross-section have individual decitex less than 2.10. The method according to claim 9, wherein the filaments with thenon-circular filament cross-section are trilobal with modification ratiogreater than 1.2 and less than 2.4.
 11. The method according to claim 2,wherein the first group of filaments is brighter than the second groupof filaments, and the first group of filaments has filaments withtrilobal cross-section and with individual filament decitex greater than2.5, has modification ratio between 1.4 and 1.7, and the second group offilaments has filaments with circular cross-section and with individualfilament decitex less than
 2. 12. The method according to claim 1,further comprising the step of texturing the mixed polyamide yarn byfalse twist texturing or airjet texturing.
 13. The method according toclaim 1, wherein the yarn has a tenacity of from about 25 to about 65cN/tex and an elongation to break of from about 20 to about 90%.
 14. Amethod of making a polyamide mixed yarn comprising: simultaneouslyspinning from separate spinning packs, a first group of filaments of afirst polyamide and a second group of filaments of a second polyamidedifferent from the first polyamide; combining the first and secondgroups of filaments through an air interlacing jet; and winding up theinterlaced filaments at a speed of at least 3000 m/min, wherein thefirst polyamide is a cationic-dye polyamide and the second polyamide isan anionic-dye polyamide; and said yarn has yarn weight from about 5 toabout 300 dtex.